Given :
Mass of neon gas at STP.
To Find :
The volume of 139.05 g of neon gas at STP.
Solution :
Molar mass of neon, M = 20 g.
Number of moles in 139.05 g of neon :
n = 139.05/20 ≈ 7 moles
We know, volume of 1 mole of any atom/molecules in STP is 22.4 L of volume.
So, volume of 7 moles of neon is :
V = 7×22.4 L
V = 156.8 L
Therefore, volume of 139.05 g of neon gas at STP is 156.8 L.